/*生成指定长度的随机数*/
function util(length) {
  var chars = ["0", "1", "2", "3", "4", "5", "6", "7", "8", "9"];
  var result = "";
  for (var i = 0; i < length; i++) {
    var index = Math.ceil(Math.random() * 9);
    result += chars[index];
  }
  return result;
}
exports.randomCode = util;
